Access gateways are widely used to connect devices in a home of a customer or devices of an enterprise to the Internet or to any other wide area networks (WAN). Access gateways use for example digital subscriber line (DSL) that enables a high data rate transmission over copper lines, or use optical fiber technology. Network operators, e.g. Network service providers (NSP), are managing a large amount of access gateways, and also other devices such as routers, switches, repeaters, wireless bridges and telephones, which are understood in this context as customer premises equipment (CPE) devices.
Access gateways including wireless technology have a key role in today's home and professional environments. A mechanism for connecting wireless devices to a local area network (LAN) is called Wi-Fi, which is a brand name of the Wi-Fi Alliance for devices using the IEEE 802.11 family of standards for wireless data transmission. The IEEE 802.11 standards define two types of wireless nodes, a general wireless device that can connect to other devices called a station (denoted as STA) and a special type of a STA that is in control of the network, namely an access point (denoted AP). A Wi-Fi network, often called a WLAN (wireless local area network), consists of an AP with one or several STA connected to the AP.
Video streaming is more and more used within LANs and WLANs, for example, for using Internet Protocol TV (IPTV). For streaming video to several end-devices, in particular multicast streaming is used, as defined by the Internet Group Management Protocol (IGMP). Providing multicast video over a wireless transmission is unreliable and has a low maximum throughput due to the definition of multicast handling in IEEE 802.11.
To extend the range of an access gateway, wireless bridges and repeaters are known. An in-house wireless video distribution system consists in an embodiment, as depicted in FIG. 1, of an access gateway 1 being connected via an Ethernet link with a wireless bridge including a bridge access point and a bridge station. The bridge station is connected via an Ethernet link with a receiver 2, e.g. a set-top box (STB). The wireless bridge is for example a video bridge in accordance with an IEEE 802.11 standard.
The receiver 2 subscribes to a video stream by sending an IGMP join message upstream via the access gateway 1 to an Internet service provider (ISP). This join message is snooped by the wireless bridge and by the access gateway 1. When received from the ISP, the access gateway 1 starts to forward the multicast video stream to the bridge access point which in turn forwards it (using unicast on layer 2) to the bridge station and further to the receiver 2. Only if an IGMP join message was seen for a certain multicast group from a specific client, the multicast stream is forwarded to that client. Hence, for all wireless devices intended to transmit multicast video over wireless, it is needed to perform a multicast to unicast conversion.
Due to the nature of the communication medium that is used, a wireless link is more easily broken than a wired link. In case of a connection loss of the wireless link, and when the wireless link is restored between the bridge access point and the bridge station, the receiver 2 has to request the multicast data stream again. Because the Ethernet links did not go down, after the connection loss of wireless link 3 and the reestablishment, no specific action is triggered in the access gateway 1 and the receiver 2. The access gateway 1 will lose all it's learnt multicast groups for that client, as it clears its connection table upon disconnection.
As a result, the multicast video stream is not restored when the client is connected again and a user interaction is needed to play the video again (e.g. to zap to same channel) or the user has to wait until the system refreshes the multicast group subscriptions (it does this periodically), so that an additional delay of the video playback is caused after restoring of the wireless link.
A gateway for a reliable multicast wireless video transmission is described in U.S. Pat. No. 8,374,113.